Upset at soldier interrupting special date (8)
I believe the answer is:
agitated
'upset' is the definition.
(thesaurus)
'at soldier interrupting special date' is the wordplay.
'soldier' becomes 'GI' (GI can mean a US soldier).
'interrupting' is an insertion indicator.
'special' indicates anagramming the letters.
'at' enclosing 'gi' is 'agit'.
'date' with letters rearranged gives 'ated'.
'agit'+'ated'='AGITATED'
(Other definitions for agitated that I've seen before include "On edge, anxious" , "Troubled, nervous" , "Panicking" , "Upset (by a stirrer?)" , "Aroused - disturbed" .)